LEDs on a String

Okay, so a friend and I got bored and decided to play with this idea. We attached a few leds to some thin string (we used dental floss), creating a pendulum. Then we turned off the lights, pointed a camera up, opened the shutter for about 25 seconds and released the led:

A 25 second exposure of a single red led.

And then we tried making a double pendulum by adding a second, green, led.